Optical modulators constructed from Si or other semiconductor materials may impart certain phase changes or “chirp” to optical signals upon which they operate. Unfortunately, chirping degrades certain transmission qualities of modulated light.
In addition, Si modulators exhibit a waveguide loss that is dependent upon refractive index change. Modulators exhibiting such index-change-dependent waveguide loss are unsuitable for use with many modulation formats that are used in advanced optical communications systems.
In an article entitled “Linearized Mach-Zehnder Intensity Modulator” authored by X. Xie, J. Khurgin and J. Kang which appeared in IEEE Photonics Technology Letters, Vol. 15, No. 4, in April 2003, the authors describe an optical modulator in which certain deficiencies were overcome, but not the undesirable chirping.